A chemically amplified positive-working resist composition is a patterning material which generates an acid on exposure to an radiation, such as far ultraviolet light, undergoes acid-catalyzed reaction to create a change in solubility in a developing solution between the exposed area and the non-exposed area thereby to form a pattern on a substrate.
A photosensitive system designed to be exposed to light from a KrF excimer laser mainly comprises a resin having a polyhydroxystyrene skeleton which exhibits a small absorption primarily at 248 nm. It is a better system than a conventional naphthoquinonediazide/novolak resin system, enjoying high sensitivity, high resolution, and satisfactory patterning performance.
When a light source of shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as an exposure source, however, the above-described chemically amplified system is insufficient because the compound having an aromatic group essentially exhibits a large absorption at 193 nm.
Use of poly(meth)acrylate as a polymer having a small absorption at 193 nm is reported in J. Vac, Sci. Technol., B9, 1991, 3357. This polymer is disadvantageous in that it has lower resistance to dry etching generally involved in semiconductor device fabrication than conventional phenolic resins having an aromatic group.
To cope with the ever increasing demands for finer patterning and higher throughput, it has now come to be important to reduce exposure errors. Conventional resists have narrow exposure latitude and considerable line edge roughness (LER), which have been a bar to increase the throughput. Further, with the recent trend toward finer dimensions of resist patterns, collapse of a resist pattern has become problematic due to a high aspect ratio of height to width of resist lines. The pattern collapse problem is particularly conspicuous with resists designed for ArF, electron beam (EB), vacuum ultraviolet (UVU) or extreme ultraviolet (EUV) radiations. The term “pattern collapse” as used herein is intended to include any pattern collapse phenomena irrespective of the causes, for example, insufficient adhesion and insufficient film strength.